1. Field of the Invention
The present invention relates to a plasma display device including a plasma display panel and a drive unit thereof.
An image display in a progressive form is superior to an image display in an interlace form from a viewpoint of luminance. Improvements of a plasma display device have been proceeding so as to realize an image display of a high resolution in a stable progressive form.
2. Description of the Prior Art
A surface discharge format is adopted for an AC type plasma display panel for a color display. Here, the surface discharge format has a structure in which display electrodes that become anodes and cathodes in display discharge for determining light emission quantity of cells are arranged on a front or back substrate in parallel, and address electrodes are arranged so as to cross the display electrode pairs.
There are two types of arrangement forms of the display electrodes in the surface discharge format. For convenience, one of the types is referred to as an individual type, and the other is referred to as a shared type. The individual type has a structure in which a pair of display electrodes is arranged for each row of a matrix display. The total number of display electrodes is twice the number of rows. The individual type can realize the progressive display by relatively simple driving sequence because each row can be controlled independently of other rows. However, an electrode gap between neighboring rows (that is called an opposite slit) becomes a non-light emission area, so a utilization factor of a screen is small. The shared type has a structure in which display electrodes whose number is the number of rows plus one are arranged at a constant pitch. In the shared type, neighboring display electrodes constitute a pair of electrodes for surface discharge, and all the display electrode gaps become surface discharge gaps. The shared type is superior to the individual type from the viewpoints of a vertical resolution (the number of rows) and the utilization factor of a screen. In either the individual type or the shared type, display electrodes making pairs are arranged in parallel, so it is necessary to provide a partition (a discharge barrier) for preventing discharge interference between cells arranged along the display electrode at least.
As a pattern of the partition, there are a stripe pattern by which a discharge space is divided into columns of the matrix display and a mesh pattern by which a discharge space is divided into columns and rows (i.e., into cells).
Conventionally, a plasma display panel having the stripe pattern partition and the shared type display electrode is driven by an interlace drive sequence, in which odd rows and even rows are lighted alternately. This driving sequence is disclosed in Japanese unexamined patent publication No. 9-160525. In addition, a variation of a shape of a display electrode in this type plasma display panel is disclosed in Japanese unexamined patent publication No. 2000-113828. In FIG. 3 of this publication a display electrode (a main electrode) that is patterned in T-shape for each cell is described, while in FIG. 11 of this publication a display electrode whose part for one row has a ladder-like shape is described. This publication also describes an effect of a band-like shape of the electrode that is cut off partially, which is that spreading of discharge in the column direction is suppressed, and that the maximum value of discharge current is decreased.
On the other hand, Japanese unexamined patent publication No. 2003-5699 describes a driving sequence for realizing a progressive form display by using a plasma display panel that has the shared type display electrodes and the mesh pattern partition that can suppress the discharge interference between rows. According to this driving sequence, rows are divided into two groups in accordance with a specific rule, addressing is performed for each group, and a reset step including charge adjustment is inserted between addressing for one group and addressing for the other group.
The progressive display according to the driving sequence described in the above-mentioned Japanese unexamined patent publication No. 2003-5699 requires a complicated control of wall charge, so it is necessary to decrease a variation of an operational condition among cells in the plasma display panel as much as possible. The variation of an operational condition causes a lighting error, which may make a display unstable. More specifically, there is a cell in which an area of the display electrode is smaller than a design value because of a misregistration of substrates that constitute a panel enclosure, a variation of a cell size depending on the partition, or the like. In such a cell, forming of charge for generating address discharge will occur insufficiently, so that a discharge start voltage for the address discharge will be higher than in other cells. In this case, the address discharge may be failed at high probability. On the contrary, a cell in which the area of the display electrode is larger than the design value will form excessive charge by the address discharge, so discharge may be generated in error in high probability.
In particular, if the plasma display panel has a larger screen and higher definition, the variation of cells becomes conspicuous, so that a stable progressive display becomes difficult to realize.